Mortality

Major impediments to producing a complete picture of Indigenous mortality in Australia are the incomplete identification of Indigenous status in death records, and the experimental nature of the recently adopted population estimates ^[1]. As a result, the 2,472 deaths registered in 2008 where the deceased person was identified as Indigenous is certainly an underestimate of the actual number of Indigenous deaths.

Assessment by the ABS of the completeness of recording of Indigenous deaths is based on a comparison of registered Indigenous deaths with the 2006 census ^[2]. The estimated completeness of identification of Indigenous people in death registrations has improved since the 1990s, mostly because of improvements in Qld and NSW. The Australia-wide Indigenous deaths notification rate in 2006-2007 was 0.92. There is a considerable variation in rates from each state and territory; WA (rate 1.11) and the NT (rate 1.09) had rates more than 1.0, indicating an over-representation of Indigenous deaths (the number of persons identified as Indigenous in death registration was greater than those identified as Indigenous in the 2006 census). NSW had a rate of 0.87 and Qld had a rate of 0.94. Vic, SA, Tas, and the ACT had small numbers of Indigenous deaths and had a group rate of 0.65. Reflecting the various levels of under-identification of Indigenous status in death registrations, caution needs to be exercised in interpretation of the figures presented in this report. It is possible that the true figures could be up to 30% higher than those presented here.

Standardised death rates

After adjusting for the differences in the age structures of the Indigenous and non-Indigenous populations and for the incomplete identification of Indigenous status in death registrations, the numbers of deaths of Indigenous people in 2000-2004 were around four times higher than the numbers expected from the age-sex-specific death rates for the total Australian populations (Table 1) ^{[3][4][5][6][7]}. (The ABS warns that the projected numbers of deaths should be interpreted with caution ^[4]. It is possible that the standardised mortality ratios (SMRs) based on the projected numbers of deaths may over-estimate the differences between Indigenous and total population mortality, but it is likely that the true ratios will be closer to these estimates than to those based solely on death registrations.)

Expectation of life

In 2009, the ABS revised its estimates for expectation of life at birth for Indigenous Australians ^[2]. The revised estimates have significantly increased the life expectancy for Indigenous males and females. Importantly, comparisons between the original and revised estimates should not be interpreted as a change in Indigenous life expectancy, but should be seen as the result of a revision in statistical methods used to calculate life expectancy.

After adjustment for the underestimate of the number of deaths identified as Indigenous, the ABS estimates that Indigenous males born in 2005-2007 could be expected to live to 67.2 years, about 11.5 years less than the 78.7 years expected for non-Indigenous males (Table 2) ^[2]. The expectation of life at birth of 72.9 years for Indigenous females in 2005-2007 was almost 10 years less than the expectation of 82.6 years for non-Indigenous females.

Age at death

For those jurisdictions with reasonable information about Indigenous deaths, the median age at death in 2008 for Indigenous males ranged from 49.0 years for those living in SA to 59.9 years for those living in NSW ^[1]. (The median age at death is the age below which 50% of people die. Because the measure partly reflects the age structures of the respective populations, it is a less precise measure than age-specific death rates, which are summarised below.) These levels are around 20 years less than those for non-Indigenous males, which ranged from 66.3 to 79.2 years. The median age at death for Indigenous females in 2008 ranged from 53.5 years for SA to 63.8 years for NSW. These levels are more than 20 years less than those for non-Indigenous females, which ranged between 75.7 and 84.6 years.

In 2006-2008 the age-specific death rates were higher for Indigenous people than for non-Indigenous people across all age groups, but the rate ratios were particularly high in the young and middle adult years (Table 3) ^[1]. (These ratios, being based on the numbers of deaths registered, are likely to underestimate the true differences between death rates for Indigenous people and the total population by around 30%.)

Infant mortality

The infant mortality rate is the number of deaths of children under one year of age in a calendar year per 1,000 live births in the same calendar year. For those jurisdictions with reasonable information about Indigenous deaths in 2006-2008, the highest Indigenous infant mortality rate was in the NT (13.6) and the lowest in SA (6.4) (Table 4) ^[1]. These rates are considerably higher than those for the total population in these jurisdictions, which range from the NT (7.8) to WA and SA (both 3.5).

Causes of death

For deaths identified as Indigenous in 2001-2005, cardiovascular disease (also known as ‘diseases of the circulatory system', which includes heart disease and stroke) was the leading cause of death for Indigenous males and females living in Qld, WA, SA and the NT (Table 5) ^[10]. The number of deaths recorded for Indigenous males was 3.2 times the number expected from the age-cause-specific rates for non-Indigenous males, and number recorded for Indigenous females 2.7 times the number expected from the age-cause-specific rates for non-Indigenous females. (See Box 1 for further information about these standardised mortality ratios (SMRs)). The estimates quoted here have not been adjusted for the likely under-identification of Indigenous people in death registration systems, so SMRs could be up to 30% higher) ^[11].

For Indigenous males, the next most frequent causes of death were injuries (including transport accidents, intentional self-harm and assault) (SMR 2.9), malignant neoplasms (cancers) (SMR 1.5), diseases of the respiratory system (SMR 4.3), and endocrine, nutritional and metabolic disorders (mainly diabetes) (SMR 7.5) ^[10]. For Indigenous females, the most frequent causes of death after cardiovascular disease were malignant neoplasms (SMR 1.6), endocrine, nutritional and metabolic disorders (SMR 10.1, external causes (SMR 3.5), and diseases of the respiratory system (SMR 3.6).

Maternal mortality

In Australia in 2003-2005 (the most recent period for which detailed data are available), six (10%) of the 60 maternal deaths where Indigenous status was known were of Indigenous women (Indigenous status was not reported in 8% of the deaths) ^[12].

Reflecting the higher rate of confinements among Indigenous women, the maternal mortality ratio for Indigenous women in 2003-2005 was 21.5 deaths per 100,000 confinements, almost three times higher than the ratio of 7.9 per 100,000 for non-Indigenous women (Table 6) ^[12]. For direct maternal deaths, the ratio for Indigenous women was 7.2 per 100,000 compared with 3.6 per 100,000 for non-Indigenous women.

References

1. Australian Bureau of Statistics (2009) Deaths Australia, 2008 Canberra: Australian Bureau of Statistics
2. Australian Bureau of Statistics (2009) Experimental life tables for Aboriginal and Torres Strait Islander Australians: 2005-2007 Canberra: Australian Bureau of Statistics
3. Australian Bureau of Statistics (2005) Deaths Australia, 2004 Canberra: Australian Bureau of Statistics
4. Australian Bureau of Statistics (2002) Deaths Australia, 2001 Canberra: Australian Bureau of Statistics
5. Australian Bureau of Statistics (2003) Deaths Australia, 2002 Canberra: Australian Bureau of Statistics
6. Australian Bureau of Statistics (2004) Deaths Australia, 2003 Canberra: Australian Bureau of Statistics
7. Australian Bureau of Statistics (2004) Experimental estimates and projections, Aboriginal and Torres Strait Islander Australians, 1991 to 2009 Canberra: Australian Bureau of Statistics
8. Australian Bureau of Statistics (2001) Deaths Australia, 2000 Canberra: Australian Bureau of Statistics
9. Australian Bureau of Statistics (2002) Australian demographic statistics quarterly: June quarter 2002 Canberra: Australian Bureau of Statistics
10. Australian Bureau of Statistics, Australian Institute of Health and Welfare (2008) The health and welfare of Australia's Aboriginal and Torres Strait Islander Peoples 2008 Canberra: Australian Bureau of Statistics and Australian Institute of Health and Welfare
11. Australian Institute of Health and Welfare (2004) Australia's health 2004: the ninth biennial health report of the Australian Institute of Health and Welfare Canberra: Australian Institute of Health and Welfare
12. Sullivan E, Hall B, King J (2008) Maternal deaths in Australia 2003-2005 Canberra: Australian Institute of Health and Welfare
13. Australian Institute of Health and Welfare (2008) Australia's health 2008: the eleventh biennial health report of the Australian Institute of Health and Welfare Canberra: Australian Institute of Health and Welfare